They have not been nicked here, and they are very effective. Solar powered yes, but with optics that mean the very bright LED light is directed almost all in one narrow cone down the road, and there are 2 emitters in the encapsulated block as well, one for forward and one back, so you have a white centre line with a red line behind you, and yellow and red edge markers on the dual carriageway. Small and with what looks like a really effective lens assembly as well concentrating the ambient sunlight onto a small solar cell, and then probably a lithium cell for energy storage. When the battery is getting low they change mode, from having a 200Hz or so pulse mode to having a 1Hz flashing mode to conserve power till daylight. They do light from sunset to sunrise though.
Still want to find one to take apart, but they are epoxied into the roadway itself in a casing.